package com.hss.thread;

/**
 * 思路是创建两个字符串a和b，再创建两个线程A和B，让每个线程都用synchronized锁住字符串
 * （A先锁a，再去锁b；B先锁b，再锁a），
 * 如果A锁住a，B锁住b，A就没办法锁住b，B也没办法锁住a，这时就陷入了死锁。
 *
 *  result
 *Lock1 running
 * Lock1 lock obj1
 * Lock2 running
 * Lock2 lock obj2
 *
 * 可以看到，Lock1获取obj1，Lock2获取obj2，但是它们都没有办法再获取另外一个obj，
 * 因为它们都在等待对方先释放锁，这时就是死锁。
 */
public class DeadLock {
    public static String obj1 = "obj1";
    public static String obj2 = "obj2";

    public static void main(String[] args) {
        Thread a = new Thread(new Lock1());
        Thread b = new Thread(new Lock2());
        a.start();
//        b.start();
    }

    static  class Lock1 implements Runnable{
        @Override
        public void run(){
            try{
                System.out.println("Lock1 running");
                while(true){
                    synchronized(DeadLock.obj1){
                        System.out.println("Lock1 lock obj1");
                        Thread.sleep(3000);//获取obj1后先等一会儿，让Lock2有足够的时间锁住obj2
                        synchronized(DeadLock.obj2){
                            System.out.println("Lock1 lock obj2");
                        }
                    }
                }
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
    static class Lock2 implements Runnable{
        @Override
        public void run(){
            try{
                System.out.println("Lock2 running");
                while(true){
                    synchronized(DeadLock.obj2){
                        System.out.println("Lock2 lock obj2");
                        Thread.sleep(3000);
                        synchronized(DeadLock.obj1){
                            System.out.println("Lock2 lock obj1");
                        }
                    }
                }
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
}

